Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752437AbZF2EKH (ORCPT ); Mon, 29 Jun 2009 00:10:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750898AbZF2EJ5 (ORCPT ); Mon, 29 Jun 2009 00:09:57 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:38858 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750759AbZF2EJ5 (ORCPT ); Mon, 29 Jun 2009 00:09:57 -0400 Date: Mon, 29 Jun 2009 06:09:54 +0200 From: Ingo Molnar To: "Figo.zhang" Cc: lkml , Andrew Morton Subject: Re: [PATCH]highmem_32.c: add argument pointer checking Message-ID: <20090629040954.GA13117@elte.hu> References: <1246244906.5759.5.camel@myhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1246244906.5759.5.camel@myhost> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1616 Lines: 48 * Figo.zhang wrote: > It had better add argument pointer checking. > > If any guys write driver want to alloc hightmem and pass a no-initial pointer, > it would be crashed. > > Signed-off-by: Figo.zhang > --- > arch/x86/mm/highmem_32.c | 4 ++++ > 1 files changed, 4 insertions(+), 0 deletions(-) > > diff --git a/arch/x86/mm/highmem_32.c b/arch/x86/mm/highmem_32.c > index 58f621e..e52e1a9 100644 > --- a/arch/x86/mm/highmem_32.c > +++ b/arch/x86/mm/highmem_32.c > @@ -31,6 +31,7 @@ void *kmap_atomic_prot(struct page *page, enum km_type type, pgprot_t prot) > { > enum fixed_addresses idx; > unsigned long vaddr; > + BUG_ON(!page); > > /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */ > pagefault_disable(); > @@ -58,6 +59,9 @@ void kunmap_atomic(void *kvaddr, enum km_type type) > unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK; > enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id(); > > + if(!kvaddr) > + return; > + (Please run patches through scripts/checkpatch.pl before submission.) Also, what's the improvement here? Before the patch we'd crash on a NULL dereference ... after the patch we'd crash on a BUG_ON(). Furthermore, he kunmap_atomic() change is outright wrong - it will now allow NULL kunmaps, which can hide bugs in drivers. Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/